Method and apparatus for producing a one-part vehicle wheel

ABSTRACT

An apparatus and a method for producing a one-part vehicle wheel are provided, in which a substantially disk-shaped, undercut-free preform is cast. Immediately after casting the preform is conveyed to a flow-forming machine, whilst maintaining a residual heat and is fixed therein. The circumferential area of the fixed preform is split and by subsequent spinning and flow-forming is constructed as an intermediate form with a rim, which already substantially has the wall thickness of the rim of the finished vehicle wheel. The intermediate form is cooled, sized and undergoes a final end-working.

[0001] The invention relates to an apparatus and a method for producing a one-part vehicle wheel with a hub and a rim.

[0002] It is known to manufacture vehicle wheels by casting. Compared with a cast workpiece as such, a higher strength can be obtained if a blank is shaped in a drop forge and is then further worked on a flow-forming machine. Such known methods are complicated and costly as a result of the tools required.

[0003] The object of the invention is to provide a method and an apparatus with which it is possible to produce simply and with high strength vehicle wheels.

[0004] According to the invention the object is achieved by a method having the features of claim 1. The invention relates to a method for the production of a one-part vehicle wheel having a hub and a rim, wherein:

[0005] a) an undercut-free, substantially disk-shaped preform is cast,

[0006] b) immediately following casting the preform is transported to a flow-forming machine, whilst maintaining a residual heat and is fixed therein,

[0007] c) the fixed preform is split in its circumferential area and by subsequent spinning and flow-forming is shaped to an intermediate form with a rim base area, which already substantially has the wall thickness of the rim of the finished vehicle wheel,

[0008] d) the intermediate form is cooled and

[0009] e) the cooled intermediate form is sized and end-worked to the finished vehicle wheel.

[0010] The design of the preform as a substantially disk-shaped, undercut-free workpiece makes it possible to use a simply constructed casting tool. Instead of a usually necessary, multipart segmental tool it is possible to use a simple, two-part casting tool. It is also possible to obviate the complicated removal of cast seams, which are unavoidable in multipart tools. The central area of the cast preform substantially corresponds to the hub of the finished vehicle wheel.

[0011] A simplification of the manufacturing process, accompanied by significant energy saving results from the immediate transportation of the cast preform to the next working step on a flow-forming machine. After casting the preform has a temperature of approximately 300° C. Particularly when using light metals it is advantageous for avoiding cracks to carry out flow-forming at an elevated temperature, which is preferably above the recrystallization temperature of the material. During flow-forming of a heated preform, the forming forces required are much lower than with workpieces at room temperature.

[0012] Compared with the hitherto known methods, in which the rim contour and wall thickness are provided with a certain allowance for the final mechanical machining, in the method according to the invention following calibration the rim base and lateral rim beads are substantially end-shaped. For the lateral areas and the formation of bores, a certain metal-removing working is required.

[0013] The method according to the invention is advantageously further developed in that the preform, after casting and prior to shaping to the intermediate shape, is supplied with additional heat. For example, the preform is heated to approximately 400° C. in a furnace, which the preform passes through on conveying from the casting equipment to the flow-forming machine. In said furnace it is merely necessary to heat from the temperature after casting to the desired machining temperature during flow-forming. Compared with heating starting from room temperature, this leads to shorter warm-up times and an improved energy balance.

[0014] According to another variant of the invention, the vehicle wheel is manufactured from a non-age-hardenable aluminium alloy, particularly Gk-Al Si 11 Mg. The intermediate form requires no additional heat treatment and can be sized directly after cooling. Cooling can take place in a tunnel-like cooling device, which the intermediate form passes through on conveying to the sizing device.

[0015] An alternative variant comprises the vehicle wheel being manufactured from an artificially ageable aluminium alloy, particularly Gk-Al Si 7 Ma Wa.

[0016] Such aluminium alloys can readily undergo noncutting shaping. In order to obtain a desired strength, following the shaping of the intermediate form a heat treatment is necessary.

[0017] The heat treatment preferably comprises the intermediate form undergoing a solution heat treatment and a quench cooling. The temperature control and duration of the solution heat treatment, as well as the speed during quench cooling are dependent on the material used. The cooling normally, takes place to room temperature.

[0018] Another variant of the method according to the invention comprises the sizing of the rim being performed by a section roller on a flow-forming machine and that the rim only mechanically undergoes end-working in its lateral areas at the rim beads. The section roller has a contour, which is the negative form of the desired contour of the rim base and rim beads. Thus, sizing can take place by a simple, radial infeeding of a section roller.

[0019] The object of the invention can also be achieved by a method having the features of claim 7. The circumferential area of a substantially disk-shaped preform is split a first time. By subsequent spinning and flow-forming an intermediate form is shaped with a radial flange and a rim base area, which already substantially has the wall thickness of the rim of the finished vehicle wheel. The radial flange is then split a second time into an outer leg and an inner leg directed towards the rim base. From the outer leg is finally shaped a rim bead and from the inner leg a roughly axially directed rim shoulder and an undercut is formed between the rim base area and the rim shoulder.

[0020] In a preferred method variant the rim bead is shaped from the outer leg and the rim shoulder from the inner leg by spinning and flow-forming.

[0021] Another advantageous method variant comprises a hump being shaped on the rim shoulder.

[0022] According to the invention an apparatus according to claim 10 is provided for achieving the object. The undercut-free castings permit a simple, problemfree manufacture of preforms. Whereas complicated castings must initially be cleaned, in the case of the invention the simple parts can be directly supplied to a flow-forming process. During transportation planned cooling and additional heating of the still heated castings leads to a desired flow-forming temperature being obtained.

[0023] The invention is described in greater detail hereinafter relative to preferred embodiments and the attached drawings, wherein show:

[0024]FIG. 1 A part cross-sectional view of a preform.

[0025]FIG. 2 A part cross-sectional view of an intermediate form.

[0026]FIG. 3 A part cross-sectional view of the intermediate form after sizing.

[0027]FIG. 4 A plan view of an apparatus according to the invention for performing the inventive method.

[0028]FIG. 5 A part cross-sectional view of a further preform for performing a method variant.

[0029]FIG. 6 A part cross-sectional view of an intermediate form following the first splitting.

[0030]FIG. 7 A part cross-sectional view of an intermediate form during shaping for forming the rim base.

[0031]FIG. 8 A part cross-sectional view of an intermediate form after the second splitting and a shaping for forming the rim base with inside rim bead.

[0032]FIG. 9 A part cross-sectional view of an intermediate form following a shaping process for forming an undercut and an outside rim bead.

[0033]FIG. 10 A part cross-sectional view of a vehicle wheel produced according to the invention with an end-shaped rim with undercut.

[0034]FIG. 1 shows a cast, substantially disk-shaped preform 11, which has a hub area 12 and an inclined circumferential area 13. In the hub area 12 are provided a central opening 14 and further openings 15. During casting the hub area 12 is shaped in such a way that, other than for a limited metal removal in the vicinity of the central opening 14, it corresponds to a hub of the finished vehicle wheel.

[0035] Immediately following removal from a mould, the preform 11 is transported to a flow-forming machine, in which the preform 11 shown in broken line form in FIG. 2 is shaped in noncutting manner to an intermediate form 21. For this purpose the preform 11 is fixed in a spinning chuck with a corresponding outer contour. The circumferential area 13 of the preform 11 is then split, so that a larger part of the circumferential area 13 is flow-formed on one side to a rim base area 22 and a smaller part to the other side to a rim bead area 23. The rim base area 22 and rim bead area 23 are constructed in such a way that they have the wall thickness of the rim of the finished vehicle wheel and require only limited sizing and reworking. The flow-forming process is performed under elevated temperature, produced on the workpiece during casting and on transportation to the flow-forming machine.

[0036] The intermediate form 21 is then cooled. This can take place in the same setting on the flow-forming machine or preferably on transporting to a second flow-forming machine, which is used for sizing the workpiece contour. As a function of the choice of material, a heat treatment, e.g. an artificial ageing can take place beforehand.

[0037] Following the cooling of the indermediate form 21, the latter is sized on a flow-forming machine, as can be gathered from FIG. 3. The intermediate form 21 shown in broken line form is fixed in a spinning chuck. A profiling roller, whose outer contour corresponds to the desired profile of a rim base 31 of a finished vehicle wheel 30 is radially infed to the intermediate form 21. The two rim beads 32, 33 are also shaped during sizing.

[0038] Finally, the shaped edges of the two rim beads 32, 33 and the area of the central opening 14 are then end-worked by material removal. The material removals represented as black surface areas are kept to a minimum, as is apparent from FIG. 3.

[0039] An apparatus 50 for performing a method variant according to the invention is shown in FIG. 4. A preform 11 removed from a mould and whose temperature is lower than the melting point of the material, but higher than ambient temperature, is conveyed by means of a conveyor belt 51 to a flow-forming station, which in this embodiment has two flow-forming machines 52, 53. On the way to the flow-forming station the conveyor belt 51 passes through a tunnel-like heating furnace 54 with which the preform 11 can be heated from its elevated temperature immediately after casting to a desired flow-forming temperature.

[0040] The heated preform 11 is removed by means of a handling device 55 from the conveyor belt 51 and is supplied to one of the two flow-forming machines 52, 53. The handling device 55 is also used for removing the shaped intermediate forms 21 from the flow-forming machines 52, 53 and for placing on a further conveyor belt 56. Alongside a buffer section 57 can be provided at the conveyor belt 56 a heat treatment station for solution heat treatment. In the represented embodiment the conveyor belt 56 passes through a tunnellike cooling device to a calibrating or sizing station 59. By means of a further handling device 60 the cooled intermediate form 21 is conveyed by the conveyor belt 56 to a flow-forming machine 61 in which sizing takes place. A mechanical end-working of the workpiece can also take place in the sizing station 59. The end-shaped workpiece is conveyed with the aid of the handling device 60 for conveying away to a further conveyor belt 62.

[0041]FIG. 5 shows another preform 11 a, on the basis of which the method according to the invention is carried out in accordance with a preferred variant. The preform 11 a comprises a finished wheel body 2, which is fundamentally radially constructed, a central opening 14 a and openings 15 a. A circumferential area 13 a is approximately symmetrically constructed with respect to a centre plane perpendicular to the centre axis 41.

[0042]FIG. 6 shows an intermediate form, which results from the preform 11 a shown in FIG. 5 as a result of the splitting of the circumferential area 13 a into two legs, a radial flange 6 and an area 17 coaxial to the centre axis 41.

[0043]FIG. 7 shows an intermediate form in which the coaxial area is made almost conical to a free end 34. The coaxial area 17 and radial flange 6 enclose a corner area 10, whose construction decisively determines the undercut 5 to be produced (cf. FIGS. 9 and 10). An inner wall 25 of the coaxial area 17 directed towards the centre axis 41 has a construction which, like the wheel body 2, corresponds to the finished vehicle wheel.

[0044] The wall thicknesses and lengths of the radial flange 6 and coaxial area 17 are dimensioned in such a way that the resulting material accumulation is suitable for the desired construction of a rim 4 (cf. FIG. 10).

[0045] In broken line form FIG. 8 shows the coaxial area 17. In continuous line form is shown a rim base 31 a with an inside rim bead 32 a in a preformed construction. The shaping of the coaxial area 17 to the preformed rim base 31 a and preformed inside rim bead 32 a takes place in a spinning device with the aid of radially adjustable, not shown spinning rollers and in particular under heat action. The rim base 31 a with inside rim bead 32 a can also be referred to as a long wheel side 9 as opposed to a short wheel side 19 (cf. FIGS. 9 and 10). In the corner area is indicated in dot-dash form a recess 20, which can optionally be formed by e.g. a material removal or spinning of the radial flange 6 in this area. This recess leads to a further weight reduction, which is particularly advantageous.

[0046] The long wheel side 9 is merely preformed by flow-forming according to FIG. 8, whereas a final profiling or finish turning is shown in FIG. 10.

[0047]FIG. 9 shows the construction of an undercut 5 between the rim base area 22 a and the rim shoulder 26 in a flow-forming machine, in that at least one, not shown splitting roller acts on the radial flange 6. As is clear from the dot-dash and broken lines of the radial flange 6, the latter is radially split, so as to form an inner leg 16 and an outer leg 18. Both legs 16, 18 are mainly symmetrically constructed, so that the splitting process can be performed performed particularly precisely. A continuous line indicates an outside rim wing 33 a and a rim shoulder 26, which are formed by spinning rollers from the outer leg 18 or inner leg 16. The outside rim bead 33 a is bent outwards, whereas the rim shoulder 26 passes substantially horizontally and axially parallel to the centre axis 41. In the vicinity of this rim shoulder 26 is located the tyre with a tyre bead. FIG. 9 clearly shows the construction of the undercut 5 and the resulting material saving and weight reduction.

[0048]FIG. 10 shows a finished vehicle wheel. A hump 27 is formed on the rim shoulder 26. The contours of the rim base 31 a, an inside rim shoulder 28, the hump 27, a further hump 29, the inside rim bead 32 a and the rim shoulder 26 in the vicinity of the outside rim bead 33 a and the undercut 5 are standardized and are obtained by machining. 

1. Method for the production of a one-part vehicle wheel (30) having a hub and a rim, wherein: a) an undercut-free, substantially disk-shaped preform (11) is cast, b) immediately following the casting the preform (11) is transported to a flow-forming machine (52, 53), whilst maintaining residual heat and is fixed therein, c) the fixed preform (11) is split in its circumferential area (13) and by subsequent spinning and flow-forming is shaped to an intermediate form (21) with a rim base area (22), which already substantially has the wall thickness of the rim of the finished vehicle wheel (30), d) the intermediate form (21) is cooled and e) the cooled intermediate form (21) is sized and end-worked to the finished vehicle wheel (30).
 2. Method according to claim 1 , characterized in that, after casting and before forming to the intermediate form (21), additional heat is supplied to the preform (11).
 3. Method according to claim 1 or 2 , characterized in that, the vehicle wheel (30) is manufactured from a non-age-hardenable aluminium alloy, particularly Gk-Al Si 11 Mg.
 4. Method according to claim 1 or 2 , characterized in that, the vehicle wheel (30) is manufactured from an artificially ageable aluminium alloy, particularly Gk-Al Si 7 Ma Wa.
 5. Method according to claim 4 , characterized in that, the intermediate form (21) undergoes a solution heat treatment and a quench cooling.
 6. Method according to one of the claims 1 to 5 , characterized in that, the sizing of the rim (31) is carried out by means of a section roller on a flow-forming machine and that the rim is only mechanically end-worked in its lateral areas at the rim beads (32, 33).
 7. Method for producing a one-part vehicle wheel (30) with a hub and a rim, particularly according to one of the claims 1 to 6 , wherein: a) a substantially disk-shaped preform (11) is split in its circumferential area and a first leg and a second leg are formed, b) by flow-forming an intermediate form (21) is formed and the first leg is shaped to a rim base area (22 a), which already substantially has the wall thickness of the rim of the finished vehicle wheel (30) and the second leg forms a radial flange (6), c) by further splitting the radial flange (6) is split into an outer leg (18) and an inner leg (16) directed towards the rim base area (22 a), d) a rim bead (33 a) is formed from the outer leg (18) and e) from the inner leg (16) is formed an approximately axially directed rim shoulder (26) and an undercut (5) is formed between the rim base area (22 a) and the rim shoulder (26).
 8. Method according to claim 7 , characterized in that, the shaping of the rim bead (33 a) from the outer leg (18) and the rim shoulder (26) from the inner leg (16) takes place by flow-forming.
 9. Method according to one of the claim 7 or 8 , characterized in that, a hump (27) is shaped on the rim shoulder (26).
 10. Apparatus for producing a one-part vehicle wheel, particularly according to one of the claims 1 to 9 , with a casting station for casting undercut-free, substantially disk-shaped preforms (11), a flow-forming station with at least one flow-forming machine (52), a conveyor means, which is located between the casting station and the flow-forming station and serves to convey the preforms (11) from the casting station to the flow-forming station, and a temperature regulating device, particularly a heating furnace, located along the conveyor means and which is constructed for setting a desired flow-forming temperature of the preforms (11) during conveying. 